Laminated electronic devices in which a tunneling electron-permeable film separates opposed electrodes



July 5, 1966 GIAEVER 3,259,759

LAMINATED ELECTRONIC DEVICES IN WHICH A TUNNELING ELECTRON-PERMEABLEFILM SEPARATES OPPOSED ELECTRODES Original Filed Nov. 17, 1960 5Sheets-Sheet 1 Fig. H93.

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United States Patent Office 3,259,759 LAMINATED ELECTRONIC DEVICES INWHICH A TUNNELING ELECTRON-PERMEABLE FILM SEPARATES OPPOSED ELECTRODESIvar Giaever, Schenectady, N.Y., assignor to General Electric Company, acorporation of New York Original application Nov. 17, 1060, Ser. No.70,074, now Patent No. 3,166,427, dated Dec. 31, 1963. Divided and thisapplication Sept. 18, 1963, Ser. No. 309,806 7 Claims. (Cl. 307-885)This is a division of my application Serial No. 70,074, filed Nov. 17,1960 (now Patent No. 3,166,427) which is a continuation-in-part of myapplication Serial No. 40,621, filed July 5, 1960, and now abandoned,both of which applications and said patent stand assigned to theassignee of this case.

The present invention relates generally to the electron tunnel emissionart and is more particularly concerned with novel tunnel devicesincluding diodes and triodes and with new circuits and systemsincorporating them, and with an unique method of making such devices.

The so-called tunnel diode of the prior art is a pm junction diodedevice which is different from the previously conventional p-n diodes inmaterial, construction and electrical characteristics. Thus, heavilydoped semiconductors are used in the tunnel diode with theconcentrations of electrons and holes more than cm." and the specificresistivity is less than 0.01 ohm-cm. When the carrier concentration isincreased in excess of 10 emf-' distribution of the carrier followsFermi statistics and the electrical properties of the semiconductorbecome metal-like.

As for its electrical characteristics, the tunnel diode of the prior arthas the interesting property of a voltage controlled negative resistancein the forward direction for low voltages and this negative resistanceis completely different from the negative resistance observed in the reverse direction of some previously known point-contact type diodes. Inthe p-type and n-type sides of the prior tunnel diode, the excessacceptor concentration and excess donor concentration, respectively, aremore than 10 cm.- (the acceptor concentration and the donorconcentration are approximately equal to the hole concentration and theelectron concentration, respectively). There is, however, no insertedintermediate layer of intrinsic and other semiconductor material betweenthe p-type and n-type sides since the p-n junction is of the abrupttype. In general, a space charge occurs at or near the plane of the p-njunction and this region is called a space charge region and it has awidth of less than 200 Angstroms (2 10' cm.) compared to the usuallymore than 1000 Angstroms width of still earlier conventional p-njunctions.

By virtue of the present invention, I have provided a novel electrontunnel emission device which even in its broadest structural definitionis as different from the tunnel diode as that device is different frompreviously conventional p-n diodes described above. Further, inaccordance with this invention, which is based upon my surprisingdiscoveries, subsequently to be described, I have provided tunneldevices which differ from tunnel diode devices known heretofore not onlyin structure but also in mode of operation and in results. Thus, thesenew devices are capable of performing functions and producing resultswhich are altogether new and different in kind from the functions andresults obtainable through the use of any previously known means ordevice. In one embodiment of this invention, for example, an electrontunnel emission triode is provided and this device is suigeneris.

In accordance with this invention, I have further provided a novelmethod for producing tunnel devices, in-

cluding both diodes and triodes, which is easy to control and carry outand is amenable to mass-production use with consistently good results.

Still further, my discoveries have enabled the development of anentirely new electronics system incorporating the novel tunnel devicesof this invention and affording unique and valuable operationalcharacteristics, uses and results. These discoveries have also enabledme to invent a refrigerator which is operative at liquid heliumtemperatures and yet is comparatively easily constructed and hasextremely modest power requirements. Further, as a result of thesediscoveries, temperatures in the liquid helium range can now be easilyand continuously determined and the superconducting state can be readilydetected in an element of a cryotron or similar device.

A specific embodiment of this invention of potentially greatsignificance is the printed circuit computer memory array. As a resultof the present discoveries, the construction of computers can thus besubstantially simplified and the cost of these devices may be materiallyreduced Without incurring any significant offsetting disadvantage.

This invention is predicated upon my unexpected and unpredicteddiscovery that the tunnel effect can, under certain criticalcircumstances, be obtained and controlled in a device comprisingseparate, independent and spacedapart conductors. I further found thatwhile only two elements are in theory necessary in such a device, athird element in the form of an insulator meeting the criticalrequirement as to continuity and permeability to tunneling electrons isas a practical matter normally an essential element of the basicstructure. In one particular embodiment of this invention, however, theinsulator may satisfactorily take the form of an air gap or even avacuum gap. Still further, I have discovered that while the thickness ofthe insulating layer or film or gap is highly critical to theconsistently satisfactory functioning of this new device, the conductorelements may within broad limits be of any desired thickness dimension.Suitably, in a laminated type of construction, the conductor elementswill be in the form of films or sheets of comparable thickness an orderof magnitude or two greater than the maximum operable thickness of theinsulating layer between them.

I have also found that this basic structure, whether laminated or not,can be supplemented or multiplied by duplication of the basic elementsto produce a device having three or more conductor elements, providingalways that the critical spacing is maintained between the conductors sothat adjacent conductors will not be dead shorted against each other,but tunneling electrons can traverse the space between those conductors.Additionally, I have found that in any of the devices including thebasic diode, electrode connections may be made in any suitableconventional manner so that the novel tunnel device may be incorporatedin an electrical circuit to perform its unique function for any of avariety of purposes subsequently to be described.

In the course of making this invention, I further discovered that thecritical spacing between conductors of my new tunnel device of thelaminated or sandwich type can advantageously be provided by a methodwhich includes as an essential step the oxidation of a thin surfaceportion of one of the conductor elements of each conductor pair in thedevice. Such an oxide film in the usual case thus will be securelybonded and held to the host metal body and provide a good basis on whichto deposit or apply the second conductor without short-ing.

Stated in the broadest terms, this embodimentof the method of thisinvention comprises the steps of form-ing a first metal film, providingan electrically-insulating, continuous but tunnelingelectron permeablecoating on said Patented July 5, 1966 first metal film, and thendepositing a second metal film. on the said insulating coating. Asindicated above, the metal films may actually be relatively heavy andthick bodies by comparison with the critically thin intermediateinsulating coating or layer.

While aluminum provides a good conductor element in these new devicesand also affords almost an ideal material for in situ production of theinsulating film or coating, there are other materials which may beemployed as equivalents of aluminum for this purpose and they may benormal conductors, superconductors or semiconductors according to thefunctional characteristics desired in the ultimate novel tunnel device.Whether aluminum or another metal or material is used, however, themethod, as those skilled in the art will understand, will be generallythe same and insulating coating will be provided suitably by oxidationof a thin sunface portion of the host or metal element. Alternatively,the insulating coating may be provided by some other reaction in whichthe metal element of the ultimate new tunnel device serves as a reagentand the reaction product is an insulator in the same way and tosubstantialy the same effect in this device that the foregoing oxidecoating is. Thus, for eXam ple, a sulfide film may be provided as aninsulator for the purposes of this invention, particularly where themetal element of the device is of copper. Copper sulfide is believed tohave a superconductive state or to resemble a superconductor state or toresemble a superconductor under certain conditions and it iscontemplated by the appended claims that a device of this invention mayinclude an insulating layer or coating component which issuperconducting at certain stages or under certain conditions of use.Similarly, selenide, arsenide, nitride, chloride, fluoride, bromide,iodide and even carbide coatings may be used in place of the oxidecoatings described above as the insulating but tunneling-electronpermeable intervening or spacing layer of the present invention devices.Also, inorganic compound coatings may be employed such as nylon, thevarious vinyl resin polymers, and in :fact any film-forming materialincluding watersoluble materials.

The second conductor will be deposited or applied or otherwise bebrought into contact, with insulating coating as the final step of themethod. Here again, there are a wide variety of conductor materials thatmay be employed and selection will be on the basis of a number ofconsiderations including the kind of device and operatingcharacteristics desired and the compatibility of the second conductormaterial with the insulating coating material under conditions ofmanufacture and use.

I have further found that the critical spacing between conductors of mynew tunnel device of the laminated or discontinuous film type canadvantageously be provided by a method which includes as an essentialstep the establishment of a plurality of separate, spaced-apart depositsor spots or islands of electrically-conducting material on an insulatingsubstrate body. In this method, the deposits are either formedseparately or individually or are laid down on the substrate surface inthe form of a continuous film from which material is removed, as byevaporation, to produce the desired islands. Alternatively, the islandsmay be formed by heat treating the continuous film to agglomerate it.Those skilled in the art will understand that the resultingdiscontinuous coating will suitably be of essentially uniform thickness,although it is contemplated that the coating components or deposits maybe built up in thickness if that may be desired for any purpose.Further, it will be understood that the discontinuous coating willdesirably extend from one edge to another of the substrate body and thuscomprise a plurality of islands forming, in effect, a chain or pathacross the substrate surface.

In a variation of this embodiment, the deposits of conducting materialmaybe deposited within a substrate body instead of on its surface, inwhich case the tunnel current will flow through intervening portions ofthe substrate body instead of through .the air gap or vacuum gap betweenislands on the substrate body surface. Further, the substrate body maybe of practically any material which is electrically non-conductiveunder the conditions of use, glass being preferred, however, because ofthe ease with which adherent metal deposits may be provided on itssurface and because of the wide temperature ranges to which glass may besubjected without signficantly changing its electrical properties or itsother physical characteristics important in the contemplated used. Theconducting materials maybe those metals identified above and metals ingeneral and likewise, copper sulfide may be employed in this embodimentof the invention.

In one embodiment of its apparatus aspect of the present invention,broadly described, comprises a first conductor, an insulator and asecond conductor in a sandwich-like arrangement, the insulator being inthe form of an electron permeable continuous film disposed between andseparating the conductors and being in contact with opposed surfaces ofthese conductors. One or both of the conductors maybe a normalconductor, or it may be a superconductor or a semiconductor underoperating conditions, depending upon the functions required Olf thedevice. Thus, the device will include means for maintaining one or bothof the conductors below its critical temperature where one or both ofthe conductors should be in the superconductive state during at least apart of the period that the device is in use. The device may furthergenerally include magnetic field generating means arranged to subject asuperconducting conductor element to a magnetic field of strengthsufficient to destroy partially, or completely the superconducting statein that element. Alternatively or additionally, the device may includemeans for flowing an electric current through a superconductingconductor element of the device to destroy partially 'or completely thesuperconducting state in that element.

As previously indicated, another embodiment of the apparatus of thisinvention in general comprises a discontinuous, e-lectrically-conductivecoating on a suitable substrate body, the components or islands of thecoating being spaced or separated from each other for electron tunnelingaction by an air gap or a vacuum gap or by material of the substratebody itself. While the spacing between adjacent islands is highlycritical, just as in the case of the sandwich construction describedabove, the relative thickness and area of the islands and the ratio oftheir masses do not have an important bearing upon either the operatingcharacteristics of the device or the electron tunnel emission resultsobtained. The islands should thus be separated by a distance of from twoto Angstroms so that tunneling electrons may travel between theseadjacent islands to produce the tunnel cur rent just as in the case ofthe laminated or sandwich embodiment.

Lead wires are suitably attached to separate islands as, for example, atopposite edges of the substrate body bearing the discontinuous coating.Consequently, whether the discontinuous coating consists of only tworelatively large islands, or a much larger number of small islandsoutlining a path across the substrate surface, a tunnel current willunder certain conditions flow between islands and in the latter case,there will be a series of such currents bridging the gaps betweenadjacent islands of the chain extending entirely across the substratebody.

The novel electric circuits of this invention in general comprise atunnel device including two conductor elements and separated by eitheran air gap or by a continuous insulating electron-permeable film bearingagainst opposed surfaces of these two conductor elements, and a powersource connected to the conductors. More specifically, in a preferredembodiment of this aspect of the invention, the tunnel device includes aconductor element which has a superconductive state and a normalresistive state. Additional-1y, this device will desirably include inputmeans effective to destroy the superconductive state of this element andthereby modify the resistance across the insulating film or air gap. Aswill be described in detail 'below, electrical apparatus and circuitsmeeting these generalized definitions may serve a wide variety of usessuch as amplifiers, negative resistance devices, infrared photongenerators and detectors, high frequency phonon generators anddetectors, computer memory components, low temperature thermometers, andcryogenic refrigerator elements.

A further and better understanding of this invention will be gained fromthe detailed description of several embodiments set forth below,reference being had to the accompanying drawings in which:

FIGURE 1 is a vertical, sectional view of a cryostat apparatus embodyinga novel tunnel device of this invention in operative relation to anelectric circuit;

FIGURE 2 is an enlarged view, partly in section, of the tunnel device ofFIGURE 1;

FIGURE 3 is a chart bearing curves illustrating electricalcharacteristics of the tunnel device of FIGURES 1 and 2;

FIGURE 4 is a chart similar to that of FIGURE 3, illustrating theeffects of temperature variations within a critical range upon theelectrical characteristics of the aforesaid tunnel device;

FIGURE 5 is likewise a chart similar to that of FIG- URE 3 depicting theefiec-t of magnetic field variations within a critical range upon theelectrical characteristics of this tunnel device;

FIGURE 6 is a chart like FIGURE 3, indicating variations in voltage at aconstant current and variations in current at constant voltage in thesaid device as the superconductive state is established and destroyed ina conductor element;

FIGURE 7 is a diagram of an amplifier circuit incorporating the presentnovel tunnel device;

FIGURE 8 is a diagram of a circuit in which the said novel tunnel devicefunctions as a negative resistor;

FIGURE 9 is a chart like that of FIGURE 3 showing how the negativeresistance characteristic is developed in the tunnel device in theFIGURE 8 circuit;

FIGURE 10 is an energy diagram illustrating the use of the device ofFIGURES 1 and 2 as an infrared gener ator;

FIGURE 11 is a diagram like FIGURE 10, illustrating the insulatingeffect of the superconductor element under a certain forbidden gapcondition relative to the Fermi level of the normal conductor element ofthe diode device of FIGURES 1 and 2;

FIGURE 12 is an energy diagram like FIGURE 11, illustrating theelectron-exciting effect of radiation applied to the normal conductor toovercome the insulating effect of the superconducting electrode;

FIGURE 13 is a view like FIGURE 2 of a tunnel triode device of thisinvention with a portion broken away for clarity;

FIGURE 14 is an energy diagram illustrating the energy levelrelationship in the FIGURE 13 device when the device is operated so thatthe middle conductor is a superconductor and showing also how thecurrent flow can be controlled through con-trolling the energy gap widthof the superconductor or its potential.

FIGURE 15 is an energy diagram illustrating the energy levelrelationship and the operating principle of another novel tunnel deviceof the present invention;

FIGURE 16 is a cross-sectional, somewhat schematic, View of apparatusvimplementing the novel method of this invention for the production ofthese new tunnel devices;

FIGURE 17 is an energy diagram illustrating the energy levelrelationship and operating characteristics of still another embodimentof this invention wherein both conductor elements of the novel tunneldevice are superconductors;

FIGURE 18 is an enlarged, cross-sectional view of a cryotronincorporating the novel device of this invention; FIGURE 19 is anotherenergy diagram showing the density of states of two conductors andillustrating the energy level relationship and the operating principleof a tunnel device of this invention in which both conductors are intheir superconducting state;

FIGURE 20 is a diagram like FIGURE 19, illustrating the efl ect of theestablishment of an electrical potential difference between the twoconductor elements;

FIGURE 21 is another diagram like FIGURE 19, showing the effect of stillfurther increasing the volt-age;

FIGURE 22 is a chart bearing a curve which illustrates the negativeresistance characteristic of FIGURE 19 couple which appears during theoperation depicted in FIGURES 19 to 21;

FIGURE 23 is a partially diagrammatic view of a low-temperaturerefrigeration apparatus of this invention;

FIGURE 24 is an energy diagram illustrating the principle of operationof the refrigeration apparatus of FIG- URE 23;

FIGURE 25 is a view like FIGURE 23 illustrating a low-temperaturethermometer of this invention;

FIGURE 26 is a wiring diagram of a new analogue computer deviceincluding a tunnel emission element of this invention;

FIGURE 27 is a fragmentary plan view of a printed circuit of thisinvention suitable for use as a computer memory array component; and

FIGURE 28 is a partially diagrammatic view of a tunnel emission deviceand circuit of this invention including a discontinuous conductor film.

As shown in FIGURE 1 in a preferred embodiment of this invention, thenovel tunnel emission device is operated at extremely low temperature.Thus, tunnel device 10 of this invention is located in a cryostat, beinglocated within the lower portion of inner Dewar flask 11 below the levelof a body of 12 liquid helium. The lower part of flask 11 is disposedbelow the surface of body 13 of liquid nitrogen contained in an outerDewar flask 14. Device 10 need not be sealed against contact with liquidhelium, although it is contemplated by the appended claims that thetunnel device may suitably be enclosed in a liquid-tight container, theimportant requirement being that the refrigeration be effective toreduce the temperature of the device below the superconducting criticaltemperature of a superconducting element.

Wires 15 and 16 connect device 10 to circuit components (not shown)outside the cryostat and including a power source and suitable output orreadout means.

Device 10, as illustrated to best advantage in FIG- URE 2, consists ofthree elements, namely, a first conductor, element 17, a secondconductor element 18 and an insulator element 19, disposed between andseparating conductors 17 and 18 and bearing against opposed surfacesthereof. Conductors 17 and 18 are shown as being thin films or sheets,but they may be in the form of rather thin strips. In any event,however, the insulator 19 must be of size and shape suflicient toprovide continuous effective insulation against normal electricalconduction between opposed surfaces of the two conductor elements.Further, insulator 19 must be thin enough that it can be penetrated byelectrons tunneling from one conductor to the other. In absolute terms,insulator 19 is in the form of a film from two Angstroms to 1000Angstroms in thickness and it will be understood that there is nopractical necessity for the insulator film' to be substantially uniformin thickness within these limits. Further, as a practical matter, I havefound that an insulator of from about 15 to 20 Angstroms in thicknesscan be readily produced in accordance with the method of this inventionand that such an insulator film will produce in the present new devicesand circuits or systems including them the unique functions and resultsstated above.

Connecting wires or electrodes 15 and 16 are suitably electricallyconnected to conductors 17 and 18 in electrode junctions indicated at 20and 21, respectively.

Although in FIGURE 2, conductors 17 and 13 are illustrated as being ofapproximately the same thickness as insulator 19, it will be understoodthat in practice the conductor elements will preferably be of greaterthickness than insulator 19 by at least an order of magnitude or two.This is a matter of preference based upon production practicabilityrather than operational characteristics, the new functions andcharacteristics of the new device being obtainable with extremely thinconductors as Well as with those which are relatively thick and massive.The critical thing, again, is the thickness and the insulatingefiectiveness of the intermediate, tunneling-electron permeable film.

Interesting and unusual characteristics of tunnel device 10 are shown inFIGURE 3, where current is plotted against voltage. Curve A representsthe current-voltage relationship in one instance over a range of abouttwo millivolts and two milliamperes when the device is operated underconditions such that conductors 17 and 18 are both in normal resistivestate. With conductor 13 being a superconductor at liquid heliumtemperature and the device being operated at a temperature below theboiling point temperature of liquid helium, curve B represents thecurrent-voltage relationship over the same voltage and ampere ranges. Asthe voltage is increased, the current flowing through the deviceincreases in direct proportion in the first case. However, with thedevice at liquid helium temperature as it is in the environmentrepresented in FIGURE 1, there is a radical departure from relationshiprepresented in curve A and as shown in curve B, substantial increases involtage do not result in proportional increases in current, particularlyin the lower portion of the voltage range.

The effect of temperature upon current-voltage rela tionship device 19at temperatures below the superconducting critical temperature ofconductor 18 is illustrated in FIGURE 4. Again curve A illustrates thenormal resistive state relationship between voltage and current indevice 10, but curve C shows the voltage-current relationship over thesame voltage range as curve A where the temperature at which device 10is operated a little below the superconducting critical temperature ofthe metal of element 18. Curve D, then, represents the voltage-currentrelationship of this device Where the temperature of operation of thedevice is still further below the superconducting critical temperatureand curve E represents the voltage-current relationship in the devicewhere the operating temperature is still lower.

The influence of magnetic field upon the voltage-current relationship ofdevice 10 is similarly illustrated in FIGURE where curve A againrepresents the normal resistive state. Curve F representsvoltage-current data gathered when the magnetic field applied to devicewas almost as high as the critical magnetic field value for element 18at the operating temperature. Curve G likewise represents data gatheredwhen the magnetic field was substantially less than that applied in thecurve F experiment, and curve H represents the voltage-current dataobtained when device 10 was subjected to a still weaker magnetic field.

It will be understood that different conductors, that is, conductors ofdifferent metals in which the superconducting state can be created, willhave qualitatively similar but quantitively different transitioncharacteristics. Consequently, in the construction of diodes and triodeslike device 10, the operating characteristics desired may within limitsbe obtained through selection of the superconducting element.

The operating characteristics of device 10 in a series circuit underconstant voltage and under constant current are indicated respectivelyby lines K and L of the chart of FIGURE 6 where curves A and Bcorrespond to those of FIGURE 3 and the coordinants are the same. Byconnecting Wires 15 and 16 to constant voltage supply (approximately onemillivolt in one case), current through insulator film 19 can be variedfrom a value approaching two milliamperes (where tline K intersectscurve A) to something less than one-half milliampere (where line Kintersects curve B). This change in the current flow through theinsulator film is due solely to the transition of the superconductorelement 18 from its normal resistive state to its superconductive stateas represented by curve B. Similarly, when wires 15 and 16 are connectedto a constant current supply (approximately one milliampere in onecase), the voltage across insulator 19 may be varied from approximatelyone-half millivolt (where line L intercepts curve A) to 1.5 millivolts(where line L intercepts curve B) as the superconductor element 18 goesfrom its normal resistive state (curve A) to its superconductive state(curve B).

Again, it will be understood from the foregoing description thattransition from the normal resistive state to the superconductive stateand vice-versa may be accomplished by subjecting device 10 andparticularly conductor 18 to varying temperatures or varying magneticfield strength, as represented by FIGURES 4 and 5. Further, it will beunderstood that the superconductive state in conductor 18 may bedestroyed by passing a current through that element even though thetemperature and magnetic field conditions are within or below thesuperconducting critical limits.

Used in a circuit to produce amplification of an input signal, thetunnel device 10 is employed as a triode, as shown in FIGURE 7, contactsbeing made to the upper and lower ends of superconducting element 18 andthe device being connected in series with a constant voltage supply 22.The signal to be amplifier, indicated as input 23, then is applied toelement 18 in its superconductive state through electrodes 24 and 25with the result that current flowing through element 18 will modify theresistance across insulator film 19 in the same general manner that theapplication of a magnetic field to the superconducting element would.The circuit is completed with resistance 27 and suitable readout oroutput means 28, as those skilled in the art will understand.

In the diagram of FIGURE 8, device 10 is employed in a circuitpossessing negative dynamic resistance. Superconducting element 18 hastwo electrode connections 29 and 30 and conductor 17 is connected to theconstant voltage supply 31. A second constant voltage supply 32 isconnected by electrode 29 to conductor 18. An input signal is providedsuitably as indicated, by an alternating current source 26 connected toelement 18.

As indicated in FIGURE 9, current varies with voltage in the FIGURE 8device in response to an alternating current signal from source 26.This, as those skilled in the art will recognize, is a negativeresistance type of function but unlike the negative resistance devicesof the prior art, this one can be regulated or adjusted to meet theneeds of any of a wide variety of circuits and circuit components. Thus,for instance, by lowering or raising the operating temperature, theextent of negative resistance may be altered. In other words, in thisway the extent of the departure from curve A can be fixed within thelimit defined by curve P, which corresponds to curve B of FIGURE 3 inthat it represents the data gathered when the superconductor was in itsmaximum superconductive condition, rather than in an intermediatecondition as represented by curve S.

The effect of the alternating current signal in the FIG- URE 8 device isto change the superconducting element 18 from its superconductingcondition to its normal resistive state and back again with each cycleof the alternating input signal. Accordingly, this input signalsupplements first one of power sources 31 and 32 and then supplementsthe other one. The amount of current flowing through element 18 variesdepending upon which of these power sources is augmented by (ordiminished by) the alternating input signal, and it is the amount ofcurrent flowing through element 18 which at any given instant determineswhether that element is superconducting or normal.

In FIGURE 10, the use of the FIGURE 2 element in an infrared generatoris illustrated. Again, the normal conductor element is identified by thereference character 17 while the superconductor shown is 18 and theinsulating film is 19. With a voltage differential established throughfilm 19 and the density of states diflferential having the upper levelof conductor 17 above forbidden gap 33 on the superconductor, electronswill tunnel through insulating film 19 and descend to the level ofconductor 18. The resultant loss of energy in the electrons thustunneling through to the superconductor element is signified by thearrow. The energy released may take the form of either infrared photonsor high frequency phonons, or both.

In FIGURE 11, the top of forbidden gap 33 of superconductor 18 is abovethe Fermi level of conductor 17. As a result, practically no currentwill flow through the device, the superconductor prohibiting electronsfrom tunneling through insulating film 19.

In FIGURE 12, the same relationship between the superconductor and gap33 on one hand and conductor 17 on the other hand, prevails as in FIGURE11. FIG- URE 12, however, due to irradiation, electrons of conductor 17are excited and raised to an energy level sufficient that they tunnelthrough insulator 19 after the manner described in connection withFIGURE 10. This irradiation may be effected by infrared photons and,accordingly, the device of FIGURE 2 may be used as an infrared detectoras well as an infrared generator simply by changing the relationship ofthe top of forbidden gap 33 of the superconductor element and the Fermilevel of the conductor.

Another tunnel device 36 of this invention is shown in FIGURE 13. Triode36 is similar to device 10, but includes an additional conductor elementand an additional insulator film. Thus, conductor elements 37, 38 and39, one or more of which may be a superconductor under certain criticalconditions, are separated in a sandwich-like construction by insulatingfilms 40 and 41. Again, the insulator films will necessarily beeffective to provide an insulating gap between adjacent conductorelements and at the same time these films will be permeable to electronstunneling from one conductor element to the other as described above inreference to tunnel device 10. Suitably, device 36 will be made in themanner to be described below and except for the additional elements,will correspond in structure details to device 10, the same latitudewith regard to relative dimensions, :particularly thickness of theconductor elements, being appropriate here as in the device in FIGURE 2.Likewise, the electrical connections, leads or electrodes are suitablyjoined to tunnel device 36 in accordance with any practice known in theart satisfying the operators requirements.

Operating characteristics of .one embodiment of the device of FIGURE 13are illustrated in the energy diagram of FIGURE 14 wherein referencecharacters are applied in accordance with the foregoing description. Theenergy gap or forbidden gap in superconductor 38 is indicated at 42, itbeing understood that in this instance, conductors 37 and 39 are normalconductors. Tunnel current is indicated by the dotted line 43. In thiscase, it will be understood that if voltage is applied to conductors 37and 39, electrons will tunnel through the insulating films and throughgap 43. At a constant voltage applied to conductor 37, the currentflowing through device 36 can be controlled by regulating the positionof the top of gap 42 of superconductor 38.

From the foregoing description, it will be apparent that the top of gap42 can be adjusted by applying a magnetic field to the superconductor,by passing a current through the superconductor, or by varying theoperating temperature of the superconductor as well as by applying avoltage to conductor 38. Regulation of voltage, current, magnetic fieldor temperature will provide control over the gap width or position. Inany of these instances, except for the application of a voltage, whichmoves the forbidden gap vertically, the tendency will be to narrow thegap in the case except where temperatures change involves reducing thetemperature of the superconductor, in which case the gap is wideneduntil it reaches a maximum value which will depend upon the metal of thesuperconducting element.

By varying the width of the forbidden gap in superconductors in devicesof this invention, these devices can be tuned. The width of the gapdetermines the frequency of the energy released through the tunnelingaction as indicated in FIGURE 10. The intensity of the energy release,i.e., the volume of the tuned output signal, will be determined by thepotential difference across the insulating film or, in other words, thecurrent flows through the device.

In still another tunnel device 44 of this invention depicted in theenergy diagram of FIGURE 15, a cathode 45, suitably of aluminum, isseparated from a thin gold film 47 by a continuous insulating film 48which, as in the foregoing cases, is electron-permeable and in this caseis suitably of aluminum oxide with thickness of about 50 to 1000An-gstroms. As the diagram indicates, the Fermi level of aluminumelement 45 stands somewhat above that of gold film 47 by virtue of thevoltage applied across insulating film. This device consequentlyoperates on the tunneling principle, electrons tunneling throughinsulating film 48 and a fraction of these electrons going through thethin gold film and escaping into the vacuum in which device 44 ismaintained in operation at room temperature. (In this instance, thedevice may replace a standard glowing emitter in a standard vacuumtube.) Further, secondary electrons are created in gold film 47 andthese can escape over the work function indicated at 49. The FIGURE 15system may be used as a cold cathode in conventional tubes with theadvantage of low noise level and high efiiciency compared with hotfilament tubes. Used as an amplifier, the system makes use of gold film47 as a grid.

Metals other than gold may be used in device 44 and preferably metals oflow work function such as sodium and the other alkali metals will beused as film 47 and suitably this film will be vapor-deposited asdescribed elsewhere herein. Similarly, as indicated elsewhere herein,metals other than aluminum and insulating films other than aluminumoxide may be used in this tunnel device. Preferably, the insulating filmshould be of a material having a high dielectric strength and thetendency for electron scattering in the device should be low.

The device represented by the energy diagram of FIG- URE 17 comprisesconductors 65 and 66, both of which have a superconductive state, and aninsulating but tunneling electron-permeable film 68. These conductorsmay suitably 'be of tantalum and lead, respectively, and film 68 may beof tantalum oxide. Under conditions of use with the conductors in theirsuperconducting states they have forbidden gaps 69 and 70, respectively.

As will subsequently be explained, under certain operating conditions,i.e., with the superconductive state established in conductors 65 and66, this FIGURE 17 device will display a negative resistancecharacteristic enabling its practical use as amplification means.Further, there is reason to believe that this device can be tuned insuch use to meet special circuit conditions and requirements. It isaccordingly contemplated that this FIGURE 17 device may be substitutedfor the tunnel diode of the prior art in a wide variety of systems andcircuits.

The FIGURE 18 device is a cryotron with which is combined an electrontunnel emission device of this invention. Actually, the cryotron and thetunnel device in this case share a common element which thus serves twopurposes or functions in the novel combination. Basically, the cryotroncomprises a film of lead 73, a film of tin 74, and insulating layer 75of SiO separating and electrically insulating the lead and tin filmsfrom each other, an aluminum body 77 and an electron-permeablecontinuous film 78 of aluminum OXide separating the aluminum body fromthe tin film.

The FIGURE 18 device may be made according to the detailed disclosuresof the method of this invention and by applying the 'SiO film and thelead film through heretofore conventional vapor deposition procedures.In a typical case, the lead film will be one micron thick and micronswide, the tin film will be 0.3 micron thick and two millimeters wide andthe SiO layer will be 0.4 micron (i.e., 4000 Angstroms) thick andconsequently impentrable to tunneling electrons.

In operation, this FIGURE 18 device as a cryotron unit will bemaintained at a temperature which is low enough that the tin and leadfilms may be in their superconductive states. The device thus may becoupled into an otherwise conventional cryotron circuit or assembly as,for example, in a computer component array, and at any time desired, thestate of tin film 74 can be readily determined. In this device, if film74 is in its superconductive state, it acts as an insulator relative toa potential applied to body 77 so that a high resistance can be measuredacross the device, i.e., through film 78. On the other hand, if tin film74 is in its normal resistive state, the resistance across the devicemay be at least an order of magnitude smaller than in the former case.Suitable connections or electrodes 80 and 81 are provided to applyvoltage from a suitable source 82 to the aluminum body and to connectthe tin film in the circuit with such power source and any desiredreadout means 83 for direct or indirect determination of electricalresistance through film 78.

Those skilled in the art will gain a further understanding of thisinvention trom the following illustrative, but not limiting, examples ofthe manner in which I have carried out the process of this invention inthe production of these new devices:

Example I With reference to FIGURE 16, I have prepared the FIGURE 11device by an evaporation and condensation technique, using a tungstenfilament as a heat source to deposit successive layers of metal on asuitable substrate body in a vacuum, in particular, a glass slide 59,three inches long by one inch wide, placed on a metal mask 51 on asuitable support (not shown) in proximity to a tungsten. filament 53connected by leads 54 and '55 to a source of power. Mask 51 has alongitudinally-extending slot one millimeter wide longer than slide sothat the slide is exposed over its full length when placed on the slidein preparation for the first deposition operation. After placing a smallamount of fine aluminum wire 57 on the tungsten filament, bell 59 isplaced over the assembly and onsupporting base 60 against which the bellseals around its periphery. By vacuum pump means (not shown), bell 59 isevacuated and a vacuum of about 10- mm. of mercury is established in thebell chamber. Then the circuit including leads 54 and is closed and thefilament is thereby energized with the result that the aluminum wire 57is vaporized to condense on the unmasked one millimeter band portion ofglass slide 50. The vaporization process is accomplished in a matter ofa few seconds and then the filament is disconnected from the powersource and air is admitted to the bell chamber. During this entireoperation, the temperature of the glass slide is essentially unchanged,that is, it remains at approximately ambient room temperature throughoutthe 1'2 experiment, the heat input through the tungsten filament beingnegligible in this respect.

A film of lead is provided by repeating the foregoing operation exceptfor turning slide 50 through relative to mask 51 and for thesubstitution of a small amount of thin lead foil for aluminum wire 57.Again the operation is accomplished rather quickly due to the fact thatthe lead foil is rapidly heated to its vaporization temperature and islikewise rapidly condensed on the aluminumcoated, unmasked portion ofslide 50. Actually, this deposition of the lead film is on a continuousbut extremely thin film of aluminum oxide and covers a one millimetersquare portion of the aluminum film previously formed on slide '50, thealuminum film and the lead film together defining on slide 50 a centeredcruciform figure extending to the four edges of the rectangular slidetop or bottom surface. The aluminum oxide film forms to the desiredthickness and continuity simply by permitting air to contact thefreshlydeposited aluminum film for a period of 5 minutes or so. Thealuminum oxidation reaction takes place at room temperature at a ratesuch that insulating films which are satisfactory for the purposes ofthis invention will consistently be formed in from 5 to 10 minutes.

Contacts or electrodes are provided by means of standard metal springclips to the metal films and slide 50, the contacts being made near thefar ends of the cruciform coating figure. The amount of aluminum and theamount of lead used (two milligrams of each) are such that the films ofaluminum and lead constituting the conductor elements of the tunneldevice were each approximately 1000 Angstroms thick.

In the actual tests performed with this FIG. 11 device, a standardsix-volt automobile storage battery was used, suitable resistance andrheostat being connected in the circuit so that one mil'livolt wasdelivered to the test device. For readout, a potentiometer and agalvanometer were used.

Example II With reference to FIG. 17, a tunnel emission device of thisinvention comprising two superconductors, namely a lead film and atantalum film may be provided by following the procedure set forth indetail in Example I above. In this instance, the tantalum foil or wireserving as the source of the vapor-deposited tantalum film is vaporizedfirst from tungsten filament 53 and then the tantalum is oxidized byadmitting oxygen to the bell chamber to form an electron-permeablecoating or film which will serve to maintain the tantalum film out ofdirect contact with the subsequently deposited lead film.

The lead in suitable form is then vaporized by the tungsten electrode,as previously described, and a lead film is deposited on the tantalumoxide coating of the lead film in the vacuum of the bell chamber. Inthis instance, the glass slide used as the superstrate body is of thesame general dimensions as in Example I and the tantalum film, the leadfilm and the intervening oxide coatin would also be of approximately thesame dimensions as the conductor film and the insulating film describedin Example I.

The operating characteristics of FIGURE 17 device will clearly bedifferent from those of the device of FIGURE 11 due to the fact thatunder the conditions of use both conductor elements would be maintainedat a temperature below their superconducting critical temperatures andthe characteristic superconductor gap would then appear on both sides ofthe insulator as the energy diagram of FIG- 'URE 17 illustrates.

Example III In still another operation embodying the method of thisinvention for the production of these new devices, a copper film may beprovided on glass slide as described in Example I. A thin film which iselectron-permeable but continuous may be provided on the exposed surfaceof the copper film formed on the glass slide. This may be accomplishedby exposing the copper to hydrogen sulfide gas at a temperature suchthat the copper will be converted in situ to cuprous sulfide to anextent corresponding to that represented by the oxide conversion of thealuminum body in accordance with Example I. Subsequently the coating oftin may be laid down on the copper sulfide film, again through the useof tungsten filament 53, tin being vaporized by the filament heat. Inthis case, it is believed that the insulating film under certaincircumstances will as a superconductor still further increase theversatility of the device for various applications.

The copper and tin films and the copper sulfide coating will again be ofthe order and magnitude of thickness set forth in Example I for thecorresponding components of the device of FIGURE 11.

Example IV Following the procedure of FIGURE 1 in providing stillanother type of electron-permeable coating or layer for separating theconductor elements of the tunnel device, a film of tantalum is vapordeposited on glass slide 50 under the vacuum conditions described inExample I. Then the slide together with its tantalum coating is dippedonce in a body of water upon which a film of stearic acid one moleculethick has been provided. The resulting stearic acid-coated tantalumdeposit is then provided with an overcoat of tin, again by thevapor-deposition technique above. As in the foregoing examples the filmthicknesses and the thickness of the intermediate coating are functionalwithin the ranges stated above for the corresponding components of theother devices specifically described and accordingly the present devicemay be expected to exhibit the characteristics of the other devices ofthis invention.

Example V Again following the procedure set out in Example I, I havemade another device of this invention by vapor depositing a film ofaluminum on a glass substrate like glass slide 50 of FIGURE 16, and thenproducing in situ an aluminum oxide coating on the aluminum film merelyby admitting air into the bell chamber to contact the freshly formedfilm. Finally, I vapor-deposited a film of gold on the aluminum oxidecoating on the aluminum film and the resulting device had the energydiagram indicated in the drawing of FIGURE 15. Again, the aluminum wasof thickness of the order of magnitude of the conductor film of ExampleI and the aluminum oxide coating and the gold film were approximately150 Angstroms thick and therefore functionally the same as thecorresponding insulating portion in the other devices of this inventionpreviously described in detail.

To test the operating characteristics of this FIGURE 15 device, Iapplied to potential of about 10 volts to it and observed a tunnelcurrent of about 10 milliamperes. I also observed that the escape(useful) current into vacuum was approximately 100 microamperes. -Incarrying out this test, I simulated the conditions in a standard vacuumtube and used the device in place of a glowing wire of the tube as theemitter or source.

The negative resistance feature of devices of this invention comprisingtwo elements in their superconducting states is illustrated in its fulldevelopment in FIGURES 19 to 22, inclusive. A device like that of FIGURE17 comprising an aluminum film 85 and a lead film 86 separated by analuminum oxide film 87 is subjected to a temperature such that bothmetal films are in their superconducting state. In F'IG-URES 19 to 21,reference character 89 represents a supply of thermally-excitedelectrons of aluminum film 85, while holes in that body are representedby reference character 90 and the empty states in lead film 86 areindicated by curve 91.

In FIGURE 19 no voltage is applied to the device and this conditionaccordingly represents the point of intersection of curve T of FIGURE 22with abscissa at the origin. Voltage in millivolts is plotted againstcurrent in m-illiamperes on this chart. Thus, there is no tunnel currentand no tendency for electrons to tunnel through insulator 87 from filmto film 86, thermally excited electrons 89 being inhibited against suchtunneling action by the opposing forbidden gap of film 86.

In FIGURE 20 voltage is applied to the device and tunneling currentflows at a rate increasing rapidly as a function of voltage, as curve Tindicates, because it becomes energetically possible for more and morethermally-excited electrons to flow. When the applied voltage increasesto one-half the difference between the two energy gaps as FIGURE 20shows, the thermally-excited elec trons flowing across insulator 87 facethe most favorable density of states condition as indicated by theasymptotic form of empty states curve 91. This means that the tunnelcurrent is flowing at a maximum, represented by point V on curve T. Asthe voltage is increased still further, as shown in FIGURE 21, thetunnel current decreases to point W on curve T because thethermally-excited electrons face a less favorable density-of-statescondition than that of FIGURE 20. Finally, when the voltage has beenincreased still further, the current will increase rapidly as curve Tindicates due to the fact that it becomes energetically possible forelectrons below the forbidden gap of conductor 85 to flow.

The bistable nature of the FIGURE 19 device is evident from the chart ofFIGURE 22 because for certain current values there are two differentvoltage values as indicated at points X and Y on curve T. Thus, thechange from point X to point Y and back again is accomplished bysubjecting this device to short current pulses of direc tion dependingupon whether the change is to be made from point X to point Y or viceversa.

Referring to FIGURES 23 and 24, the low temperature or cryogenicrefrigerator of this invention includes as the central element the newsuperconducting diode 93 which comprises a non-superconducting film 94on a glass plate 95, an insulating layer 96 and a superconducting metalfilm 97 spaced from film 93 by the insulating layer. This diode, asthose skilled in the art will understand, meets the requirements setforth above for devices of this invention, particularly as to thecritical thickness and continuity of the insulating, but tunnelingelectronpermeable layer. This apparatus further includes a closed shell99 providing a refrigeration chamber 100 in which diode 93 is disposed.Shell 99 is constructed for immersion in a refrigeration liquid such asa body of liquid helium 101 in a suitable vessel 102 and is constructedto maintain a vacuum in chamber 100 for protracted periods A of suchimmersion. Diode 93 is connected by wires 105 and 105, suitably ofsuperconducting metal such as lead, to a battery 108 and a switch 109,the wires being sealed at points Where they enter housing 99 so that thevacuum in chamber 100 is maintained and liquid helium is prevented fromentering the chamber during operation of this apparatus.

In use the FIGURE 23 apparatus will be arranged generally as shown,chamber'100 being evacuated by any suitable means prior to immersion ofshell 99 in the refrigerating liquid. Objects to be refrigerated will beplaced in the chamber prior to the evacuation and may be in closeproximity to diode 93 for maximum refrigeration effects. With switch 109closed, electrons will tunnel from conductor 94 into superconductor 97as FIGURE 24 indicates. Expressed mathematically, the tunnelingelectrons will have an energy of approximately E-eV+E when they enterthe superconductor, whereas they will have an energy of onlyapproximately E when they are introduced into conductor 94.Consequently, heat will be removed from conductor 94 at the rate of[Qe-V]I, where I is the current. The electrons introduced into thesuperconductor may lose their energy mainly either by phonon emission,of if they are very stable in the excited state of the superconductor,they will lose their energy far from the diode junction. A calculationof the maximum possible heat removal based upon a resistance of 10- 15ohm/cm. for insulator 96 is Q- watts/cm. at 42 K., the efficiency ofthis process being proportional to temperature, as those skilled in theart will understand.

The low temperature thermometer of this invention illustrated in FIGURE25 again includes diode 93 as the central element. In this instance,however, since refrigeration is not desired, the .diode may be disposedin the body of liquid helium 101, in a vessel 102, suitable electricconnections being made to the conductors 94 and 97 to determine thetemperature in the bath through the current and voltage relationshipexisting in the diode. Thus, wires 118, 111, 112 and 113, suitably ofsuperconducting metal such as lead, connect the diode to a battery 115and amrneter 116 and voltmeter 117. By this means the voltage is appliedto conductor 94 as in the FIGURE 23 circuit and in addition a voltmeter117 is coupled across the diode. Accordingly, when switch 119 of FIGURE25 apparatus is closed, current flowing through the diode is measured onammeter 116 and at the same time the volt age across the diode ismeasured on voltmeter 117.

The current flowing through the insulating film of this device variesexponentially with the applied voltage over a rather wide voltage range.For voltages in the approximate range -kT/e V '2kT)/e, where k isBoltzm-ans constant, e is electronic charge, T is temperature K), and Eis half the energ gap in a superconductor. Since at any particulartemperature E is a constant, the following relationship exists -eConsequently, if we plot enI versus V the slope of the straight line isl/kT and gives an absolute measure of the temperature. If the currentand voltage have been determined at one particular temperature, use mayalso be made of the fact that the energy gap is nearly constant for lowtemperatures and plot to obtain the temperature corresponding to anyother temperature occurring at that voltage.

Referring to FIGURE 26, the present new superconducting diodes isemployed in a computer to obtain an analogue function or result and inthe embodiment shown, the computer will multiply. The fact that anyparticular temperature T for voltages greater than kT/e but smaller than(E2kT)/e the current depends exponentially on voltage makes the devicevery useful. In this case with e the electronic charge and E being halfthe energy gap, the following holds true, Z-e as previously herein setforth. Accordingly, it will be understood by those skilled in the artthat by itself this new diode device is naturally suited for exponentialfunctions and natural logarithms. Its use in this way in a simplecircuit is illustrated in this drawing wherein 120 is a conventionaladder and 121, 122, and 123 are superconducting diodes of thisinvention. Current inputs to this circuit are indicated at 125 and 126,while the output representing the product of the two current inputs isindicated at 12 The printed circuit of FIGURE 27 comprises a pluralityof the novel tunnel diodes of this invention and is suitable for use ina variety of ways. It is contemplated, for example, that this kind ofprinted circuit application of this invention may be used as a memoryarray in a computer, replacing more expensive components and assembliesknown heretofore in the art.

In this device a metal film 130 is applied to a glass plate 131,suitably by means of the evaporation techniques described in detailhereinabove. An insulating film of critical thickness in accordance withthis invention is likewise formed on the surface of deposit 130 inaccordance with the method described above. Then a. series ofsuperconducting metal films 133, 134, 135, 136 and 137 are deposited onplate 131 and are extended to overlie the insulating coating on deposit130. These superconducting metal films, as shown, may normally beseparate and spaced apart from each other so that they may functioncompletely independently of each other in the system into which theFIGURE 27 device is coupled. These superconducting metal films, it willbe understood, will likewise advantageously be deposited by theprocedure previously described in detal herein, so that this device can"be made economically and with high accuracy and may even be adaptableto mass production techniques. If desired, lead wires may be provided bythe vapor deposition or printing technique although in the FIGURE 27.embodiment metal films 133 to 137, inclusive, each serve the doublepurpose of second metal component of the diode sandwich and ofelectrical lead.

The device of FIGURE 27 was made in accordance with the followingillustrative, but not limiting, example:

Example VI Using the apparatus of FIGURE 16 equipped with two separatetungsten filaments having separate electric power connectors andfollowing the general procedure set forth in Example I, a strip ofaluminum foil was vaporized from one of the filaments and aluminum wasvapor deposited on an exposed or unmasked portion of glass plate 131 toproduce film 130. This vapor depositon was carried out under a pressureof 5X10 mm. of mercury. The vacuum was then relieved to the extent thatthe pressure was increased to about 50 microns of mercury by admittingair into bell 5?. After a period of 10 minutes at this higher pressureand with the desired insulating, but tunneling electron-permeable, oxidefilm having been formed over the entire surface of strip 130, theoriginal vacuum was re-established in the bell and lead was similarlyvaporized from the other filament and thus vapor deposited on plate 131which was partially unmasked so that the separate film strips 133 to137, inclusive, could be simultaneously deposited. Relief of the vacuumwas not necessary prior to vaporizing the lead foil, mechanical meansbeing provided for accomplishing the unmasking and being operated from alocation outside bell 59 through a pressure sealing gland. The vacuumwithin the bell was then completely relieved and the FIGURE 27 devicewas removed and subjected to tests and found to exhibit the negativeresistance characteristic and the bistable property hereinabovedescribed.

In FIGURE 28 the tunnel diode device of this invention representing thealternative to the FIGURE 2 device previously described comprises asubstrate body 140, suitably a glass plate, and a plurality of separateand individual, spaced-apart islands of superconducting metal 141.Islands 141 While shown to be of uniform size and shape may be of randomsize and shape without materially effecting the operation of the deviceor the results obtained through its use. The critical thing, aspreviously stated herein, is the spacing between islands 141, this beingof the order of magnitude of from two Angstroms to Angstroms. Like thesandwich device exemplified in FIGURE 2, a potential is applied to thisFIGURE 28 diode by means of a battery 143 connected by lead wires 144and 145 to opposite ends of the island chain across plate 140. A tunnelcurrent under certain circumstances previously described will then flowbetween adjacent islands 141 and a series of such tunnel currents willcooperate to bridge the distance across plate 1411..

Having thus described this invention in such full, clear, concise andexact terms as to enable any person skilled in the art to which itpertains to make and use the same, and having set forth the best modecontemplated of carrying out this invention, I state that the subjectmatter which I regard as being my invention is particularly pointed outand distinctly claimed in what is claimed, it being understood thatequivalents or modifications of, or substitutions for, parts of thespecifically described embodiments of the invention may be made withoutdeparting from the scope of the invention as set forth in what isclaimed.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. An electronic device comprising a laminated body, means forconnecting the body in an electric circuit, and means for maintainingthe laminated body at a temperature such that an element of said bodywill be superconducting, the said laminated body comprising asemiconductor in the form of a film, a second conductor in the form of afilm of metal which is superconducting within a certain temperaturerange, and a continuous film of insulating material disposed between andengaging the semiconductor and the superconductor and through whichelectrons can tunnel in travel from one of said conductors to the other.

2. An electronic device comprising a first metal film, a second film ofmetal having a superconductive and a normal state, a continuous film ofinsulating material from two to 100 Ansgtroms thick disposed betweenopposing surfaces of the said metal films and spacing the metal filmsapart while being pervious to tunneling electrons traveling from onesaid metal film to the other, means for maintaining the temperature ofthe second metal film below the superconducting critical temperature ofthe metal of said second film, and magnetic field generating meansarranged to subject the said second metal film to a magnetic field ofsufiicient strength to destroy superconductivity in the metal of thesecond film.

3. An electronic device comprising a first metal film, a second film ofmetal having a superconductive and a normal state, a continuous film ofinsulating material from two to 100 Angstroms thick disposed betweenopposing surfaces of the said metal films and spacing the metal filmsapart while being pervious to tunneling electrons traveling from onesaid metal film to the other, means for maintaining the temperature ofthe second metal film at a level such that the said film may besuperconducting, and means for passing an electric current through thesecond metal film to destroy the superconducting state therein.

4. An electric circuit comprising an electron tunnel emission deviceincluding a superconducting element and a normal metal element and acontinuous insulating but electron-permeable film from two to 100Angstroms thick separating the said elements, and a power sourceconnected to the superconductive element and to the normal metal elementof the tunnel device, and input means including an input signal sourceconnected across the superconducting element to cause current to flowthrough the superconducting element and modify the resistance across theinsulating film of the said tunnel device.

5. An electric circuit comprising an electron tunnel emission deviceincluding a superconducting element and a normal metal element and acontinuous insulating but electron-permeable film from two to Angstromsthick separating the said elements, a power source connected to thesuperconducting element and to the normal metal element of the tunneldevice, and input means including an input signal source effective todestroy the superconductive state of the superconducting element andthereby modify the resistance across the insulating film of the tunneldevice.

6. An electric circuit comprising a tunnel device including asuperconducting element and a normal metal element and a continuousinsulating but electron-permeable film from two to 100 Angstroms thickseparating the said elements, a first power source connected to thesuperconducting element and to the normal metal element of the tunneldevice, and a second power source connected across the superconductingelement to cause current to flow through the superconducting element andmodify the resistance across the insulating film of the tunnel device.

7. An infrared energy generator comprising a tunnel device including asuperconductor element and a normal metal element and a continuousinsulating but electronpermeable film from two to 100 Angstroms thickseparating the said elements against direct physical contact with eachother, a power source connected to the said superconducting element, andthe said normal metal element, and means for maintaining the tunneldevice at a temperature below the superconducting critical temperatureof the superconducting element.

References Cited by the Examiner UNITED STATES PATENTS 1,900,018 3/1933Lilenfeld 317235 2,273,704 2/ 1942 Grisdale 317235 2,619,443 11/ 1952Robinson 1l7--200 2,858,239 10/ 1958 Nitsche 117--200 2,900,531 8/1959Wallmark 3 17235 2,970,449 2/ 1961 Eichhorn 623 2,973,441 2/1961Courtney-Pratt 307--88.5 3,010,285 11/1961 Penn 62-3 3,021,433 2/ 1962Morrison 30788.5 3,024,140 3/1962 Schmidlin 31723 3,056,889 10/1962Nyberg 30788.5 3,060,327 10/1962 Dacey 317235 FOREIGN PATENTS 1,060,8817/ 1959 Germany.

JOHN W. HUCKET, Primary Examiner.

ARTHUR GAUSS, Examiner.

J. D. CRAIG, Assistant Examiner.

1. AN ELECTRONIC DEVICE COMPRISING A LAMINATED BODY, MEANS FOR CONNECTING THE BODY IN AN ELECTRIC CIRCUIT, AND MEANS FOR MAINTAINING THE LAMINATED BODY AT A TEMPERATURE SUCH THAT AN ELEMENT OF SAID BODY WILL BE SUPERCONDUCTING, THE SAID LAMINATED BODY COMPRISING A SEMICONDUCTOR IN THE FORM OF A FILM, A SECOND CONDUCTOR IN THE FORM OF A FILM OF METAL WHICH IS SUPERCONDUCTING WITHIN A CERTAIN TEMPERATURE RANGE, AND A CONTINUOUS FILM OF INSULATING MATERIAL DISPOSED BETWEEN AND ENGAGING THE SEMICONDUCTOR AND THE SUPERCONDUCTOR AND THROUGH WHICH ELECTRONS CAN TUNNEL IN TRAVEL FROM ONE OF SAID CONDUCTORS TO THE OTHER. 